1. Field of the Invention
The present invention relates to a microwave oven, and more particularly to an AC/DC type microwave oven, which is capable of using an AC (alternating current) power or a DC (direct current) power selectively.
2. Description of the Background Art
The microwave oven is an appliance for heating/cooking food using a microwave. In the microwave oven, a high voltage transformer steps up a common power source 120/230V of the AC power to a high voltage of 2,000V, and a magnetron driven by the high voltage 2,000V produces a microwave having a predetermined frequency. The microwave oscillates molecules of water in food, and then food is heated/cooked by the generated heat.
FIG. 1 is a partial cutaway perspective view of a conventional microwave oven.
In FIG. 1, the reference numeral 1 is a cabinet, the reference numeral 2 is a cooking chamber, and the reference numeral 3 is a device chamber. The reference numeral 4 is a door, the reference numeral 5 is a tray, and the reference numeral 6 is a cover. The cabinet 1 is partitioned into left and right spaces. At one side of the cabinet I is provided the cooking chamber 2 of which front is open. At the other side of the cabinet 2 is provided the device chamber 3 in which a variety of electrical devices are installed.
At the upper and side of the cabinet I is provided the cover 6 that forms the appearance of the microwave oven. The door 4 is fixed to one side of the cabinet I which is capable of pivoting so that the front of the cooking chamber 2 can be opened/closed thereby. The tray 5 is installed at the bottom of the cooking chamber 2, and food to be cooked is loaded on the tray 5. The tray 5 is rotated by a driving motor(not shown) installed at the lower side thereof.
The reference numeral 7 designates a control panel. The reference numeral 8 designates an air guide, and the reference numeral 9 designates a cooling fan. HVT, HVC, HVD and MGT designate a high voltage transformer, a high voltage condenser, a high voltage diode and a magnetron, respectively. They are installed in the device chamber 3, and are connected electrically with each other. The high voltage transformer HVT transforms a common alternating current AC into a high voltage, and the high voltage is doubled by the high voltage condenser HVC and the high voltage diode HVD (which is 4,000V approximately). Then, the doubled high voltage is applied to the magnetron MGT, and then a 2,450 MHz (megahertz) microwave is generated by the magnetron MGT.
The control panel 7 is installed at the front side of the device chamber 3, through which a user operates the microwave oven, and the operational state of the microwave oven is displayed.
The cooling fan 9 cools the magnetron MGT and the high voltage transformer HVT by blowing forced air. The air guide 8 is installed near the magnetron MGT so that the air heated during the cooling operation of the magnetron MGT is guided into the cooking chamber 2.
FIG. 2 is a block diagram of AC/DC type microwave oven according to the prior art, and FIG. 3 is a schematic diagram of FIG. 2.
In FIG. 2, AC/DC type microwave oven according to the prior art includes an AC driving load 10, a DC driving load and DC/AC converting part 20, and a microwave oscillator 30.
The AC driving load 10 is driven by an AC input power. The DC driving load and DC/AC converting part 20 include the DC driving load being driven by a DC input power and the DC/AC converter converting the DC input power into an AC power. The microwave oscillator 30 is inputted by the power out of the AC input power or the DC/AC power converted by a DC/AC converter, and generates a 2,450 MHz (megahertz) microwave.
With reference to FIG. 3, a schematic diagram of AC/DC type microwave oven is described as follows.
In FIG. 3, the AC input power is connected to the AC driving loads 11, and is connected to a power switch SW1 to determine the driving status of the AC power. The AC driving loads 11 include a lamp 12a and a cooling fan motor 12b being operated by an AC power. The DC power is connected to the DC driving loads 21, and is connected to a power switch SW2 to determine the driving status of the DC power, and forms a differential DC circuit net discriminated as an AC circuit net. The DC driving loads include a lamp 22a and a cooling fan motor 22b being operated by a DC power.
The DC input power is connected to the DC/AC converter 23. The microwave oscillating part 30 includes a high voltage transformer HVT which receives both the AC power and the DC power, a high voltage condenser HVC, a high voltage diode HVD, and a magnetron MGT. The operation of the microwave oscillator is described the same way as shown in FIG. 1.
The operation of a conventional microwave oven having the above-described constitution is as follows. First, the user pulls the door 4 so that cooking chamber 2 is opened, then places a container containing food on the tray 5. The user closes the door 4, switches-on the power switch SW1 or the power switch SW2 selectively, and then operates the microwave oven. The user, however, must switch on only one of the DC power switch SW2 or the AC power switch SW1 according to the input power described. For example, in case the user switches on the AC power switch SW1, the AC input power supplies to the driving load that includes the lamp 12a and the cooling fan motor 12b. The AC input power also supplies to the high voltage transformer HVT of the microwave oscillating part 30. When the AC power supplied to the high voltage transformer HVT is converted to a high voltage through the high voltage condenser HVC and the high voltage diode HVD, the high voltage is supplied to the magnetron MGT. The magnetron MGT driven by the high voltage generates a microwave. The generated microwave radiates it into the cooking chamber 2 for the heating/cooking of food, and then radiates it into food uniformly when the tray 5 is rotated in the cooking chamber 2. In the device chamber 3, the cooling fan 9 cools the inner devices by blowing air. The tray 5 rotates the food in order to radiate the microwave on the food uniformly. Therefore, the food in the cooking chamber 2 is heated/cooked properly according to the cooking time and cooking temperature that have been selected by the user.
In case the user switches on the DC power switch SW2, a DC input power supplies to the driving load that includes the lamp 22a and the cooling fan motor 22b, and supplies to the DC/AC converting part 23. The DC/AC converting part 23 converts the DC input power into an AC power, and then the converter AC power supplies to the high voltage transformer HVT of the microwave oscillating part 30. After the converted AC power supplied to the high voltage transformer HVT is converted to a high voltage by the high voltage condenser HVC and the high voltage diode HVD, the high voltage is supplied to the magnetron MGT. The magnetron MGT driven by the high voltage generates a microwave. The generated microwave radiates it into the cooking chamber 2 for the heating/cooking of food.
In such a conventional AC/DC type microwave oven, the microwave oven must be provided with the differentiated driving loads for AC and DC, respectively. As the number of parts of the microwave increases, the manufacturing cost of the microwave oven increases.
Furthermore, in case the AC power and the DC power are selected by the user the same time mistakenly, a conventional microwave oven increases the possibility of faulty operations since a conventional microwave oven cannot prevent such an occurrence.
The present invention has been made to overcome the above described problem of the prior art, and accordingly it is the first object of the present invention to provide an AC/DC type microwave oven for reducing the manufacturing cost of the microwave oven by reducing the number of parts of the driving loads that include a lamp and a cooling fan motor driven by the AC power.
It is the second object of the present invention to provide an AC/DC type microwave oven to prevent the faulty operations of the microwave oven by limiting the selection of only one of the AC power and the DC power available.
To achieve the above objectives, the present invention provides an AC/DC type microwave oven comprising: means for selecting an AC input power or a DC input power; means for supplying power using a common driving load being driven by the DC power, and supplying the AC input power or a DC/AC converted power selected by the means for selecting; and means for oscillating the microwave being driven by the AC power supplied by the means for suppling power.
The means for selecting comprises: one more exchanging switch for supplying a circuit net with only one of the AC input power or the DC input power available, when the AC input power and the DC input power form an AC circuit net and a DC circuit net, respectively, which are discriminated from each other.
The one more exchanging switch includes: a first exchanging switch being connected to a common line of the AC and DC circuit nets; a second exchanging switch being connected to the AC circuit net; and a third exchanging switch being connected to the DC circuit net.
The means for supplying power includes: a rectifying part for rectifying the AC input power into a DC power; driving load being driven by the rectified DC power or the DC input power; and DC/AC converting part for converting the DC input power into AC power.
The rectifying part includes: a low voltage transformer to step-down the AC input power; and a bridge diode for rectifying the step-down AC input power into DC power.
The DC/AC converting part is a rotatable inverter for producing an AC power according as the DC power inputted in one direction is outputted in turn in two directions. The rotatable inverter includes: a motor being driven by the DC input power; and a commutator for producing an AC power according to the DC input power being inputted in one direction is outputting in turn in two directions by means of input/output brushes being contacted with four directions of the commutator and being rotated by the motor.
To achieve the above objectives, the present invention provides an AC/DC type microwave oven including: means for rectifying the AC input power into a DC power; a driving load being driven by a rectified DC power or the DC input power; a rotatable inverter including a motor being driven by the DC input power, and a commutator for producing an AC power according to the DC input power being inputted in one direction is outputting in turn in two directions by means of input/output brushes being contacted with four directions of the commutator and being rotated by the motor; and a microwave oscillating part for being driven by the AC input power or the AC power converted by the rotatable inverter.
The means for rectifying includes: a low voltage transformer to step-down the AC input power; and a bridge diode for rectifying the step-down AC input power into DC power.
The means for selecting includes: one more exchanging switch for supplying a circuit net with only one of the AC input power or the DC input power, when the AC input power and the DC input power form an AC circuit net and a DC circuit net, respectively which are discriminated from each other.
The one more exchanging switch includes: a first exchanging switch being connected to a common line of the AC and DC circuit nets; a second exchanging switch being connected to the AC circuit net; and a third exchanging switch being connected to the DC circuit net.
Accordingly, an AC/DC type microwave oven adopts the only driving load driven by the DC power, reduces the number of parts of the AC driving load that include a lamp and a cooling fan motor driven by the AC power, and reduces the manufacturing cost of the microwave oven. Besides, the AC/DC type microwave oven can prevent the faulty operation by means of entering selectively only one of the AC power or the DC power.